1. Field of the Invention
This invention relates to an inspecting method of an electronic component having a plurality of lead rows, each comprising a plurality of leads arrayed in a line along and protruding from a face of the main body thereof, and mounting method of the same onto a substrate.
2. Prior Art
When electronic components, such as QFP and SOP, having plural leads protruding outward from each face thereof are mounted onto substrates, it is usually necessary to perform an inspection prior to the mounting operation for checking the defectiveness of configuration of each component. The mounting operation of the electronic components, such as QFP and SOP, is usually carried out in the following manner. A substrate having electrodes applied solder (or solder paste) thereon is prepared in advance. The leads of the electronic component are landed onto their corresponding electrodes of the substrate, thereby mounting the electronic component on the substrate. The substrate mounting the electronic component is subsequently heated and later cooled down to provide a permanent rigid connection between the leads and their corresponding electrodes. In this soldering operation, if any lead is extraordinarily deformed in an up-and-down direction among plural leads arrayed in a line, an open-circuit defect will possibly arise. To avoid such a failure, it is definitely necessary to conduct an inspection prior to the mounting operation of the electronic component onto a substrate, for checking the presence of an extraordinary deformation of lead in the up-and-down direction (i.e. a floating of lead) and omitting or abandoning the defective components if found in this inspection so as not to be soldered onto the substrate.
One of conventional lead inspecting methods is carried out in the following manner. Of plural leads of an electronic component, only three leads are chosen as representative thereof. Respective heights of these three leads are measured, and a virtual plane including these three altitudinal points is obtained. Then, other leads are compared with this virtual plane to obtain a floating amount (i.e. vertical deviation) of each lead with respect to the given virtual plane. Then, each of the floating amounts obtained is compared with a predetermined allowable value, to omit or abandon defective electronic components.
However, according to such a conventional lead inspecting method, there is a possibility that at least one of the selected three leads is extraordinarily deformed compared with other leads, resulting in that an obtainable virtual plane is fairly deviated from an ideal virtual plane and the reliability of inspection results is so worsened.
Furthermore, many of recent electronic components are thinned in thickness. Thus, the main body itself of an electronic component may cause a deformation which possibly induces an open-circuit defect as well as presence of extraordinarily deformed leads. In this respect, the conventional lead inspecting method is not so effective to overcome the above-described problems, and therefore cannot always assure an accurate detection of defectiveness of an electronic component.